In the belted radial ply tires, especially which has a stiff belt, e.g. steel belt, the ground pressure distribution is liable to become uneven, and uneven wear is liable to be caused between the tread crown and tread shoulders.
In general, the amount of wear in the tread shoulders is larger than that of the tread crown.
Such uneven wear between the tread crown and tread shoulders is considered to be caused by the curved tread profile. That is, the tread has a difference in diameter between the tread crown and tread shoulders, and this causes a slip against the ground so that the tread shoulders are worn earlier than the crown.
In order to reduce such unevenwear, for example, to increase the radius of curvature of the tread profile, to increase the size of blocks in the tread shoulders to increase the rigidity thereof, and to increase the rigidity of the belt particularly in the tread shoulder regions have been proposed, but cannot solve the problem satisfactorily.
Further, an excessive increase in the shoulder block rigidity or the belt rigidity is liable to cause other problems, namely to increase tire noise and to deteriorate ride comfort.